The child was subjected to months of torture that included being forced to smoke cannabis, and died after being struck so hard in the stomach that his liver and pancreas split in half.
Loffley was found guilty of murder at the High Court at Auckland after a trial in November last year - exactly a year after the little boy's death.
He was sentenced this morning.
JJ's aunt, Danielle Ruhe, told the court that she carried photos of JJ on her phone to keep the toddler close to her.
"Losing my nephew has had a traumatic effect. To sit through the trial and hear what my young nephew went through has shattered my life."
She referred to Loffley as a "monster" and asked what baby JJ could have done to be treated so badly.
"JJ was only ever guilty of being a precious little boy."
Details of the two-year-old's short violent life were discussed in court today.
Crown prosecutor Phil Hamlin said there was a high-level of "brutality, cruelty and callousness" in the murder.
Born James Joseph Ruhe Lawrence, and known as JJ, the child had already suffered 32 injuries, including two broken arms by the time he died.
"It certainly shows the child's life was fraught," Mr Hamlin said.
Joel Loffley began a relationship with JJ's mother, Josephine Lawrence, in 2011. While in Loffley's care JJ received two arm breaks - one left for days as Ms Lawrence was too drunk to seek help - and numerous other injuries.
Loffley "played rough" with JJ and was seen making him smoke an asthma inhaler full of marijuana.
JJ was visibly terrified of Loffley, and on the day he died, he did not want to stay with Loffley while his mother went out.
As Ms Lawrence went to leave the house to organise a bank overdraft, JJ followed her. He wanted to go with her but Loffley was insistent JJ stay behind.
"Leave that boy with me. That boy is mine today," he told her.
JJ died wearing just a nappy. After Loffley delivered the fatal blow he tucked the little boy into bed and left him to die.
Photographs of the house show how little JJ had in life. His bed was just a base with no mattress and it was strewn with his little clothes.
In the next room, where Loffley and Ms Lawrence slept, police found a large wooden blade with a handle at least half a metre long stashed behind a chest of drawers. This blade, Ms Lawrence told them, had been used on JJ by Loffley.
Violence seemed to be commonplace in the household and at only 14kg, JJ was very vulnerable against a solid and menacing Loffley.
Ms Lawrence told Loffley's trial that she was scared of Loffley, that if she didn't do what she was told she would get "a hiding".
She wasn't even safe on her birthday in September last year. Loffley smashed her in the face with his elbow, bruising her badly. In a photo taken that day Ms Lawrence used JJ to hide the bruising, holding him up in front of the injured half of her face.
Around the same time she penned sadly prophetic words on a piece of paper outlining the impact Loffley's physical abuse had on her and JJ.
"I am scared for my son ... afraid for my son's welfare ... scared he's going to be hurt and taken away," she wrote as part of an exercise set for an anger management course Loffley had to attend after beating her.
Loffley maintains his innocence.
His lawyer Roger Chambers said Loffley regrets that he did not do more to "protect the child".
- Edward Gay, APNZ court reporter
